Voltage variable resistors

ABSTRACT

A voltage variable resistor comprising a sintered wafer consisting essentially of zinc oxide (ZnO) and, as an additive, lanthanum oxide (La2O3) and/or yttrium oxide (Y2O3) and two electrodes applied to opposite surfaces of said sintered wafer, at least one of said two electrodes being a silver paint electrode. The voltage variable resistor modified with lanthanum oxide (La2O3) and/or yttrium oxide (Y2O3) has the electrical properties thereof improved by the further addition of cobalt oxide (CoO) and manganese oxide (MnO).

United States Patent Masuyama et al. [4 1 June 13, 1972 VOLTAGE VARIABLE RESISTORS Referenws Cited [72] Inventors: Takeshi Masuyama, Osaka; Toshiold UNITED STATES PATENTS f'f Osaka- 3,503,029 3/1970 Matsuoka ..317/238 x 3,529,218 9/1970 Nitta et al..... [73] Assignee: Matsushlta Electric Industrial Co., Ltd., 6,856 6/1968 Noorlander...

Kadoma, Osaka, Japan 3,419,759 12/1968 Hayakawa..... 3,505,574 4/1970 Long et al ..3l7/238 [22] 1970 3,299,332 1/1967 Saburi ..3l7/238 x [2|] App]. No; 10,959

Primary Examiner-John W, Huckert I 3"] Fords" Appnmflon Pflomy Dam Assistant Examiner-Wdlmm D. Larklns Attorney-Wenderoth, Llnd & Ponack Feb. 24, 1969 Japan.... 44/14792 March 7, 1969 Japan.... 44/18238 57 ABSTRACT Aug. 15, 1969 Japan... 44/65498 1 Aug. 15, 1969 Japan... 44/65500 A voltage variable resistor comprising a sintered wafer con- Aug. 15, I969 Japan.... ...44/65501 sisting essentially of zinc oxide (ZnO) and, as an additive, Aug. 15, 1969 Japan... .L..44/65502 lanthanum oxide 1.3 0 and/or yttrium oxide (7/ 0,) and two electrodes applied to opposite surfaces of said sintered wafer, at least one of said two electrodes being a silver paint [52] U.S. Cl. ..317/238, 317/234 L, 3l7/235 AP, electrode. The voltage variable resistor modified with 317/235 AQ lanthanum oxide (Lagoa) and/or yttrium oxide (Y O has the [51] Int. Cl ..l-l01l 3/22 electrical properties thereof improved by the further addition [58] Field of Search ..317/238, 235 AP, 235 AQ of cobalt oxide (C00) and manganese oxide (MnO).

' 8 Claims, 1 Drawing Figure 382 3); {TY ,Z fi}T-'Z;j a I PKTENTEDJUN x 3 m2 INVENTORS TAKESHI MASUYAMA TDSHIOKA AMEMIYA YOSHIO IIDA fl/mdwul iid gf/ zac ATTORNEYS The present invention relates to muffler constructions and has particular reference to a muffler which is specifically designedforuse injconnection with the-internal combustion engine of a model airplane, especially competition type model airplanes which are radio controlled from the ground. Still morespecifically, the invention is concerned with an expansion type mufiler or exhaust silencer which, when operatively installed on a model airplane engine andthe airplane is in flight, is disposed directly in the slipstream of the airplane propeller and depends upon well known phenomena associated with airfoil design for its successful operation.

It has long been recognized that when the'upper surface of an airplane wing is arched in the transversedirection of the wing, maximum aerodynamic advantage is obtained. This advantage resides principally in the fact that as the wing moves forwardly through the slipstream, the air is deflected upwardly by-the leading side of the arch,thereby creating a vacuum above the wing in the trailing camber region. The vacuum thus produced creates unbalanced forces on opposite sides of the wing, such forces being relied upon largely for wing lift and the phenomena involved is generally known as the airfoil principle.

Accordingto the present invention, the improved model airplane mufiler is of symmetrical airfoil design, which is to say that both .the upper and lower sides thereof are arched in airfoil fashion and, in effect, constitute a tubularstructure which is of tear drop design in transverse cross section. This tubular structure is closed at its opposite ends by means of tear drop shaped endwalls, thus defining an internal, maximum volume, full length, full heightand fullwidth expansion 5 chamber. The muffler is so designed and-installed on a model airplane engine that it projectsradially outwardly from the en'- gine cylinder and the exhaust gases leaving the engine cylinder enter thej'expansion chamber through the inner end wall and are expanded inthe chamben'These expanded gases leave the expansion chamber through a series of outletports which are formed in the camber regions of the muffler at locations'where theyare in direct register with the vacuum areas above and below the muffler. .These vacuum areas, acting through the outlet ports'assist in drawing the. expanded gases from the chamber and, in so doing, they not only decrease the noise level involved due to gas evacuation, but also reduce the'back pressure on the engine to a Iar'gedegree. While, the exact causes of such reduction in noise level may not atthe present time be thoroughly understood, it is believed that the reduction takes place at the precise moment when the expanded pulsating gases emerge from the outlet openings and enter a region of high vacuum where sound waves are devoid of a strong'carrier medium or, stated otherwise, a sound source air at atmospheric pressure.

will not yield as high a decibel factor in rarefied air as it will in It is not the aim of the present invention to produce a muffler. having a noise reduction factor which is so great that the sound of the emerging gases is nearly inaudible, as is the case with ordinary: automobile mufflers. In such an instance the muffler would be practically valueless for model airplane use where it is necessary for the ground operator to'memorize the sound of his own particular craft and identify it when the craft pleasing quality in that it is devoid of any objectionable trumpet action as is the case with many conventional model airplane mufflers.

weight, consisting as itdoes of three light gauge stainless steel sheet metal pieces cut to shape and silver soldered together along certain meeting edges.

A further and important object of the invention is to provide a mufiler which is possessed of a high heabdissipating factor, such object being attained by the use of the aforementioned stainless sheet material for the muffler walls. With such high heat-dissipating qualities for the muffler as a whole, a cool running engine will be the obvious result.

- Yet another object is to provide a novel muffler mounting including an angular muffler manifold by means of which the muffler proper may be cause to assume an out-of-the-way position when it is applied to a side mounted engine.

The provision of a model airplane muffler which is extremely simple inits construction, consisting-as it does largely of sheet metal stampings and which therefore may be manufactured at a low cost; one which is rugged and durable and which therefore will withstand rough usage; one which is possessed of no moving parts, internal or external and which therefore is unlikely to get out of order; one which is of compact design and therefore consumes but little space, either on the shelf or when packaged for shipping; one which offers no-appreciable windresistance when the aircraft with which it isused is in flight; one which is easily applicable to and removable from a wide variety of different engine designs; one which is attractive in its appearance and pleasing in its design; and one which, otherwise, is well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood.

In the accompanying drawings forming a part of this specification, several illustrative embodiments of the invention have embodying the principles of the present invention and showing the same operativeIy-installed on a model airplane engine;

' FIG. 2 is a front perspective view of the structure shown in FIG. 3 is a fragmentary top plan view of the inner the mufller and its adapter and clamping assembly;

FIG. 4 is an' end elevational view of the structure shown in FIG. 3, the adapter strap being broken away in the interests of clarity; i

- FIG. 5 is a front inside mufflerperse; 1

FIG. 6 is a rear outside top perspective view of the mufiler;

FIG. 7 is a top plan view of the mufiler;

FIG. 8 is an outside end elevational view of the muffler;

FIG. 9 is a front mid-plane elevational view of the muffler;

FIG. 10 is an outside rear mid-plane perspective view of the muffler;

FIG. 11 is an exploded perspective view of the muffler and its associated adapter plate and clamping assembly;

FIG. 12 is a sectional view, entirely schematic in its representation, illustrating certain aerodynamic principles which are involved in connection with the operation of the portion of mid-plane perspective view of the present muffler;

The provision of a novel 'model airplane muffler of the character brieflyoutlined above constitutes the principal ob ject of the present'invention. An additional object of the invention is to provide a muffler which is extremely light in Referring now to the drawings in detail, and in particular to FIGS. 1 and 2, a preferredform of model airplane muffler embodying the principles of the present invention is designated in its entirety by the'reference numeral 10 and it is shown as being operatively applied to a conventional model airplane ensame, the present muffler being readily applicable to a wide variety of engine constructions. The engine selected for environmental purposes herein embodies the usual crankcase 16 from which there projects vertically upwardly a cylinder 18. A crankshaft 20 which is rotatable in the crankcase 16 is associated with the usual connecting rod and piston (not shown), the latter being reciprocable in the cylinder 18. The forward'end of the crankshaft threadedly receives thereon a clamping nut and hub assembly 23 by means of which a propeller (not shown) may be fixedly secured to the crankshaft. Other conventional engine components are a cylinder glow plug 22 at the top of the cylinder 18, a carburetor 24 which receives fuel from a fuel line 26, a throttle or fuel adjustment rod 28, and other combustion engine components the details of which have not been disclosed herein.

A tubular extension 29 projects laterally from one side of the cylinder 18 in the medial region of the latter and defines an elongated slot-like exhaust port 30 for the combustion gases issuing from the engine. This exhaust port 30 communicates through an adapter block or plate 32 (see also FIGS. 3 and 11) with the muffler 10 in a manner and for a purpose that will be set forth in detail presently.

Considering now the specific character of the muffler 10, this muffler is in the form of a lightweight hollow stainless steel member of tapered tubular construction and which is closed at its ends. The muffler involves in its general organization a top wall 34, a bottom wall 36, an outer end wall 38 (FIGS. 6, 7, 8 and 10), and an inner end wall 40 (FIGS. 4, and 11). Both the top wall 34 and the bottom wall 36 are of airfoil shape or design, the top wall 36 being arched upwardly with the extreme crest of the arch lying forwardly of the central longitudinal axis of the tubular muffler as indicated by the broken line 42 in FIGS. 6, 7 and 8. The bottom wall 36 is similarly arched downwardly. The muffler is tapered on a small slant angle.

Because of the dual or symmetrical airfoil shape of the muffler as described above, the leading side thereof is curved as indicated at 44 in FIGS. 2, 5 and 8 with fairly large increments of cuuvature prevailing, while the trailing side of the muffler presents a relatively sharp and linearly straight knife edge 46.

As previously stated, the tubular muffler is of tapered design and, therefore, the inner end wall 40 is appreciably larger than the outer end wall 38, both walls being generally of tear drop configuration in outline.- The inner end wall 40 is flat or planar while the outer end wall 38 is preferably, but not necessarily, curved so that it bulges outwardly as clearly shown in FIGS. 6 and 7, the shading of this wall in FIG. 6 representing the bulge. It is however within the purview of the present invention to construct, the muffler so that the outer end wall 38 is planar and generally parallel to the wall 40, in which case the muffler will assume the form of a tapered frustum.

As best seen in FIGS. 4, 5 and 11, the inner end wall 40 is formed with a linearly straight row of muffler inlet ports 49, five such ports being shown herein although a greater or a lesser number of such ports may be employed if desired. These ports 49 lie on the major axis of the tear drop shaped end wall 40 and they are designed for register with the exhaust port 30 (FIG. 2) of the cylinder 18 when the muffler 10 is installed on the engine 12. The outer end wall 38 is imperforate.

As clearly shown in FIGS. 1, 2 and 6 to 10 inclusive, the top wall 34 of the muffler 10 is fonned with a row of relatively small outlet ports 50, the row extending in the longitudinal direction of the mufiler and being disposed an appreciable distance rearwardly of the aforementioned crest 42 of the arched portion of the top wall 34 so that the ports lie well within the chamber area of the airfoil shaped wall. Although six such outlet ports 50 have been disclosed herein, it will be understood that a greater or a lesser number of such ports may be provided if desired. Preferably this row of ports is disposed in the outer region of the muffler remote from the inlet ports 49. A similar row of outlet ports 51 is provided in the bottom wall 36 and they are similarly positioned.

Installation of the muffler 10 on an engine such as the engine 12 is effected by means of the aforementioned adapter plate 32, together with a clamping strap or band (FIG. 11) the nature of which will be described presently. The adapter plate 32 may be in the form of either a casting or a machined part and it is in the form of an elongated narrow strip of metal,

preferably aluminum of approximately square cross section I and having a centrally disposed slot 54 extending transversely therethrough. One side of the adapter plate 32 fits flat against the inner end wall 40 of the muffler 10 when the adapter plate is installed thereon with the slot 54 embracing all of the muffler inlet ports 49 in the end wall 40. The opposite side of the adapter plate 32 is recessed at the rim region of the slot, thus providing a shallow seating or pilot socket into which the outer rim region of the tubular extension 29 projects so that the exhaust port 30 registers with the slot 54, and consequently with the ports 49 in the muffler end wall 40.

In order to removably clamp the muffler 10 in its operative position on the engine 14, a U-shaped clamping strap or band 60 (FIGS. 1, 2 and 11) having parallel side legs 62 and a connecting bight portion 64 is provided. The outer ends of the sidev legs 62 are turned laterally outwardly away from each other to provide a pair of attachment ears 66. A pair of clamping screws 68 and 70 project through a pair of holes 72 which are provided in the attachment cars 66, through a pair of bores 74 formed in the end regions of the adapter plate 32, and also through similar holes 75 which are provided in the end wall 40, these screws being threadedly received by nuts 76 (FIG. 3) which are welded to the inside face of the muffler wall 40. The clamping screw 70 also passes through an alignment collar or sleeve 78 which is welded to one of the cars 66. The curvature of the bight portion 64 of the clamping strap 60 is comformable to that of the cylinder 18 of the engine 12 and the strap partially encircles the cylinder at approximately the level of the tubular extension 29 when the strap is in position on the cylinder so that upon tightening of the clamping screws 68 and 70, the muffler 10 is drawn hard against the rim of the tubular extension 29 and the exhaust port 30 communicates with the interior of the muffler through the adapter plate and in sealing relationship. In this position of the muffler 10, the longitudinal axis of the latter extends horizontally and projects radially outwardly from one side of the cylinder 18.

Structurally, the muffler 10 is of extremely lightweight construction, it being constructed in the main of relatively thin stainless steel sheet stock having a thickness on the order of 0.015 inches. The muffler lends itself to ease of manufacture in that the top wall 34 and bottom wall 36 are of unitary onepiece construction and are formed from a single blank of the stainless steel sheet metal. The blank is folded, so to speak, so as to bring the opposite ends thereof together to form the sharp trailing edge 46, after which they may be silver soldered together. Thereafter, the tear drop shaped end walls 38 and 40 are soldered in position to close the ends of .the thus formed tubular symmetrical airfoil structure. The outer end wall 38 is formed of stainless steel sheet material similar to that which forms the top and bottom walls 36 and 38, while the inner end wall 40 is formed of somewhat thicker stainless steel material which may be on the order of 0.035 inches in thickness. It will be understood of course that the various openings 49, 50, 51 and 75 are punched or otherwise fonned in the sheet metal stock prior to assembly of the three constituent parts of the muffler.

The thus assembled muffler 10, which is comprised of three sheet metal stampings, produces a symmetrical airfoil shape which defines an internal expansion chamber of maximum volume.

It is to be noted at this point that, as shown in FIGS. 1 and 2, the muffler 10 projects radially and horizontally from the TABLE 1 Silver nintA Sil i lzfliqa 2013 (C MnO lam! I mo. Ill). n10. (moi. at (3 :t ZnO (moLperccnt) percent) percent) percent) percent) 100 uni.) 1i 0 1nn.) 1i

in the same manner as that of Example 1. The'lappe d disc is coated on one surface thereof with the same silver electrode paints as those used in'Example l by a conventional brushing method. The coated disc is fired at the temperature listed in Table 2 'for 30 minutes in air. The fired disc is provided on another surface thereof with an ohmic electrode by means of spraying of aluminum or evaporating of aluminum.

Lead wires are attached to the silver electrodes by means of silver paint. The electrical characteristics of the resultant-resistor and of other similarly prepared resistors are shown in Table 3, wherein electrical characteristics are measured with a polarity in which the high voltage terminal is the silver electrode.

It will be easily realized that the combination of the silver electrode and ohmic electrode results in a low Cand a high-n:

EXAMPLE 3 Sintered discs having the compositions listed in Table 4 are prepared in the same manner as that in Example I. The sintered discs are 10 mm in diameter and 1.5 mm in thickness after lapping. Various silver electrode paints are applied to the opposite surfaces of the sintered discs and fired at the temperatures listed in Table 4 for 30 minutes in air. The silver electrode paints have solid ingredient compositions shown in Table 4 and are prepared by mixing 100 weight parts of said solid ingredient compositions with l to 20 weight partsof epoxy resin in 20 to 40 weight parts of butyl alcohol. The resultant resistors exhibit desirable C values and n values as indicated in Table 4. It will be readily understood that the electrode compositions have a great effect on the electrical characteristics of the resultant voltage variable resistors and particularly electrode compositions containing cobalt oxide and manganese oxide result in a higher value of n.

EXAMPLE 4 Sintered discs having compositions listed in Table 5 are made into resistors in the same manner as that of Example 1. The resistors are tested according to the methods used in 'testing electronic component parts. The load life test is carried out at C ambient temperature at 1 watt rating power for 500 hours. The heating cycle test is carried out by repeating five times a cycle in which said resistors are cooled to 20 C and then kept at such temperature for 30 minutes. After the 70 heating cycle and load life tests, the percentage change in the C valueand n value are shown in Table 5. It will be easily realized that the percentage changes are less than 10 percent and especially the composition of silver electrodes containing cobalt oxide and manganese oxide result in excellent properties with respect to stability. 

2. A voltage variable resistor according to claim 1 wherein one of said electrodes is a silver paint electrode and the other is an ohmic electrode.
 3. A voltage variable resistor according to claim 1 wherein said sintered wafer consists essentially of zinc oxide (ZnO) and 0.2 to 3.0 mole percent of at least one oxide selected from the group consisting of lanthanum oxide (La2O3) and yttrium oxide (Y2O3).
 4. A voltage variable resistor according to claim 1 wherein said sintered wafer consists essentially of zinc oxide (ZnO), 0.2 to 3.0 mole percent of at least one oxide selected from the group consisting of lanthanum oxide (La2O3) and yttrium oxide (Y2O3) and 0.1 to 3.0 mole percent of at least one oxide selecteD from the group consisting of cobalt oxide (CoO) and manganese oxide (MnO).
 5. A voltage variable resistor according to claim 1 wherein said silver electrode has a composition consisting essentially of 70 to 99.5 wt. percent of silver, 0.3 to 27 wt. percent of lead oxide (PbO), 0.05 to 15 wt. percent of silicon dioxide (SiO2) and 0.05 to 15 wt. percent of boron trioxide (B2O3).
 6. A voltage variable resistor according to claim 1 wherein said silver electrodes have a composition consisting essentially of 70 to 99.5 wt. percent of silver, 0.3 to 27 wt. percent of bismuth oxide (Bi2O3), 0.05 to 15 wt. percent of silicon dioxide (SiO2) and 0.05 to 15 wt. percent of boron trioxide (B2O3).
 7. A voltage variable resistor according to claim 1 wherein said silver electrode has a composition consisting essentially of 70 to 99.5 wt. percent of silver, 0.3 to 27 wt. percent of lead oxide (PbO), 0.05 to 15 wt. percent of silicon dioxide (SiO2), 0.05 to 15 wt. percent of boron trioxide (B2O3) and at least one member selected from the group consisting of 0.05 to 6.0 wt. percent of cobalt oxide (CoO) and 0.05 to 6.0 wt. percent of manganese oxide (MnO).
 8. A voltage variable resistor according to claim 1 wherein said silver electrode has a composition consisting essentially of 70 to 99.5 wt. percent of silver, 0.3 to 27 wt. percent of bismuth oxide (Bi2O3), 0.05 to 15 wt. percent of silicon dioxide (SiO2), 0.05 to 15 wt. percent of boron trioxide (B2O3) and at least one member selected from the group consisting of 0.05 to 6.0 wt. percent of cobalt oxide (CoO) and 0.05 to 6.0 wt. percent of manganese oxide (MnO). 